Contents

The United States discovered 2,4-dichlorophenoxyacetic acid (2,4-D) during World War II. It was recognized as toxic and was combined with large amounts of water or oil to function as a weed-killer. Army experiments with the chemical eventually led to the discovery that 2,4-D combined with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) yielded a more potent herbicide.[1] It was found that 2,4,5-T was contaminated with 2,3,7,8-tetrachlorodibenzodioxin (TCDD), commonly called "dioxin". Researcher Alvin Lee Young found that samples of 2,4,5-T in Agents Pink and Green had doubled the TCDD concentration of Agents Purple or Orange.[2]

Professor Nguyen Thi Ngoc Phuong, at Từ Dũ Obstetrics and Gynecology Hospital is pictured with a group of handicapped children, most of them victims of Agent Orange.

In Vietnam, the early large-scale defoliation missions (1962-1964) used 8,208 gallons of Agent Green, 122,792 gallons of Pink, and 145,000 of Purple. These were dwarfed by the 11,712,860 gallons of Orange (both versions) used from 1965 to 1970. Agent White started to replace Orange in 1966; 5,239,853 gallons of White were used. The only agent used on a large scale in an anti-crop role was Blue, with 2,166,656 gallons used.[10] The bombardment occurred most heavily in the area of the Ho Chi Minh Trail.[1]

The Rainbow Herbicides damaged the ecosystems and cultivated lands of Vietnam, and led to buildup of dioxin in the regional food chain.[1] About 4.8 million people were affected.[11]

In addition to testing and using the herbicides in Vietnam, Laos and Cambodia, the US military also tested the "Rainbow Herbicides" and many other chemical defoliants and herbicides in the US,[12] Canada, Puerto Rico, Korea, India, and Thailand[13] from the mid-1940s to the late 1960s. Herbicide persistence studies of Agents Orange and White were conducted in the Philippines.[14] The Philippine herbicide test program which was conducted in cooperation with the University of the Philippines, College of Forestry and was also described in a 1969 issue of The Philippine Collegian, the college's newspaper.
Super or enhanced Agent Orange was tested by representatives from Fort Detrick and Dow chemical in Texas, Puerto Rico, and Hawaii and later in Malaysia in a cooperative project with the International Rubber Research Institute.[8] Picloram in Agent White and Super-Orange was contaminated by Hexachlorobenzene (HCB) a dioxin-like carcinogen.[citation needed] The Canadian government also tested these herbicides and used them to clear vegetation for artillery training.[15]

A 2003 study in Nature found that the military underreported its use of rainbow herbicides by 2,493,792 U.S. gallons.[11]

Vietnam remains heavily contaminated by dioxin-like compounds, which are classified as Persistent Organic Pollutants. These compounds remain in the water table and have built up in the tissues of local fauna. However, the contamination has begun to deteriorate, and the forest canopy has regrown somewhat since the Vietnam War.[1]

^Fryer, J. D.; Blackman, G. E. (January 1972). "Preliminary Proposals for the Study of Persistence of Herbicides in Forest and Mangrove Soil". NAS committee on the effect of Herbicides in Vietnam. National Academy of Science, (NAS).Missing or empty |url= (help)